In a frictional hinge device, a diameter-increased section 11 of a rotation shaft 10 is formed so that the surface roughness (Ra) is 0.05˜0.20 &mgr;m in the circumferential direction, and the surface roughness (Ra) in the axial direction is 0.15˜0.30 &mgr;m. A relationship between a deviation “P-P” and an innermost dent V is defined as P-P<2.5 &mgr;m and V<1.0 &mgr;m. With the use of synthetic resin (PC, PAR, PPS, e.t.c.), a support block 20 is provided integrally around the rotation shaft 10. The support block 20 tightly engages with the rotation shaft 10 due to a residual stress based on a shrinkage allowance appeared when molding the synthetic resin. With a good deviation “P-P”, a shallower innermost dent V and a smaller surface roughness in the circumferential direction, a stable surface friction is maintained for an extended period time with the least amount of wear. By making the surface roughness (Ra) in the circumferential direction smaller by 0.1˜0.2 &mgr;m than the surface roughness (Ra) in the axial direction, the stable torque is positively insured with no initial scratch and no stickslip.
Legal claims defining the scope of protection, as filed with the USPTO.
1. A frictional hinge device comprising: a shaft member having a rotational axis as a rotational center; a support member which rotationally supports said shaft member, said support member being made of a synthetic resin molded around said shaft member integral therewith so that said shaft member can rotate accompanied with a surface frictional resistance between said support member and said shaft member due to a shrinkage allowance therebetween; said shaft member having such a deviation from a geometrical circular form as expressed by P-P<2.5 m and V<1.0 m; and a surface roughness Ra of said shaft member being 0.15-0.30 m in an axial direction so as to obtain a torque holding rate of 80% or more of an initial torque when said support member is subjected to repetitive rotational operation, wherein P-P is defined by a difference between an outermost shift position and an innermost shift position with respect to a referential center geometrical circle of an outer surface of said shaft member, and V is a dent of said innermost shift position with respect to a true geometrical circle of the outer surface of said shaft member.
2. A frictional hinge device comprising: a shaft member having a rotational axis as a rotational center; a support member which rotationally supports said shaft member, said support member being made of a synthetic resin molded around said shaft member integral therewith so that said shaft member can rotate accompanied with a surface frictional resistance between said support member and said shaft member due to a shrinkage allowance therebetween; said shaft member having such a surface roughness Ra in a circumferential direction as expressed by Ra 0.05-0.20 m; and said shaft member further having a surface roughness Ra of 0.15-0.30 m in an axial direction so as to obtain a torque holding rate of 80% or more of an initial torque when said support member is subjected to repetitive rotational operation.
3. A frictional hinge device comprising: a shaft member having a rotational axis as a rotational center; a support member which rotationally supports said shaft member, said support member being made of a synthetic resin molded around said shaft member integral therewith so that said shaft member can rotate accompanied with a surface frictional resistance between said support member and said shaft member due to a shrinkage allowance therebetween; said shaft member having such a deviation from a geometrical circular form as expressed by P-P<2.5 m and V<1.0 m; a surface roughness Ra of said shaft member being 0.05-0.20 m in a circumferential direction; and a surface roughness Ra of said shaft member being 0.15-0.30 m in an axial direction so as to obtain a torque holding rate of 80% or more of an initial torque when said support member is subjected to needed times of repetitive rotational operation, wherein P-P is defined by a difference between an outermost shift position and an innermost shift position with respect to a referential center geometrical circle of an outer surface of said shaft member, and V is a dent of said innermost shift position with respect to a true geometrical circle of the outer surface of said shaft member.
4. A portable business machine into which the frictional hinge device as set forth in any one of claims 1 - 3 is used to pivotably move a display thereof.
Cooperative Patent Classification codes for this invention. Click any code to explore related patents in that topic.
December 22, 2000
October 21, 2003
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